The present invention is directed to an apparatus for collecting liquid leakage in the region of a filling pipe located within a dome pit where the pipe discharges through a dome cover into an underground storage tank for fuel, heating oil and the like.
In the past, the storage of fuels has resulted in considerable environmental damage, especially with the initial use of single wall tanks. Such tanks develop leakage after a relatively short period of use because of rust. More recently the problem with single wall tanks has been relieved by utilizing double wall tanks. The routine overfilling of the tanks has also been prevented by regulations requiring overfilling safety devices or limit value indicators.
After the introduction of the above mentioned safety means, the most frequent and unpleasant damage experienced in underground tanks results from spillage or leakage. When the filling hose located in a transport vehicle is detached from the filling tube fixed to the tank in the ground, a residual quantity of liquid escapes from the filling hose and such liquid leakage, especially fuel or heating oil, is mixed with water almost always present in the dome pit. The water seeps into the dome pit through the pit sidewalls during rainfall or when it is raining or when snow melts the water enters the dome pit through the pit cover located at the surface of the ground in which the tank is located. As a result, after filling the tank and detaching the filling hose, the liquid spilled combines with the water located in the pit and is more or less rapidly transported by diffusion into the ground water. Seepage into the ground or the ground water often causes environmental damage, such as ground water contamination, and the removal of such contamination involves extraordinarily high costs. Ground water contamination can be increased by the liquid leakage or seepage flowing over the external insulation of the tank, whereby apart from damaging the insulation and possible causing rust damage to the tank outer wall, other noxious material from the insulation may enter the ground water.